Roof Design
Objectives:-
- Create a car roof model based on the styling surface master sections given for various parts with mastic points & rein forcements.
- Determine whether the design is complying with heat distortion criteria through curvature study on the roof.
- Check section modulus of front roof rail, rear roof rail ,bow roof rails and bow roof center.
- Draft analysis of all parts for checking tooling feasibility.
Roof:-
An automobile roof or car top is the portion of an automobile that sits above the passenger compartment, protecting the vehicle occupants from sun, wind, rain, and other external elements. Because the earliest automobiles were designed in an era of horse-drawn carriages, early automobile roofs used similar materials and designs.
Design Of Roof:-
- Given master section for design of roof
Front roof rail:-
Bow roof rail:-
Reinforcement center:-
Rear roof rail:-
- Roof:-
- Front Roof Rail :-
Creation of front roof rail:
Used given master section and followed following steps to created front roof rail.
- Bow roof-1
Creation of bow roof-1:
For creation followed master section and following steps
- Center bow with reinforcement
creation of center bow with reinforcement:
We have master section for creation of center bow and reinforcement. followed master section and following steps.
Center reinforcement:-
Center bow roof:-
- Rear roof rail :-
- Roof Assembly :-
- Sections Of all components:-
- Draft analysis
Roof:-
Front roof rail :-
Bow roof-1:-
Center bow roof with reinforcemet:-
Bow roof-2:-
Rear roof rail:-
Calculations to determine position of bow roof
we have,
Bow – roof prediction Formula
W = [1.73 x 10^(-3) x L] + [1.85 x 10^(-8) x (R^2)/t] + [ 1.10x10^(-3) x l] - 2.68
Judgement Condition : OK< 2.7> 3.1
Where
L = Roof Length in X-Direction[mm](Roof dimension in 0-Y)
R = Roof curvature
R = 2(Rx*Ry)/(Rx+Ry)
Rx = X curvature
Ry = Y curvature
t = Roof plate thickness [mm]
l = Bow Roof Span [mm]
|
Postion |
Rx |
Ry |
R |
R^2/t |
L |
t |
l |
w |
Status |
|
Front roof-bow roof-1 |
3303.403 |
14540.338 |
5383.691 |
38645505.04 |
2027.095 |
0.75 |
302.285 |
1.874 |
OK |
|
Bow roof-1-center bow roof |
4008.709 |
10449.913 |
5794.513 |
44768507.87 |
2027.095 |
0.75 |
362.426 |
2.053 |
OK |
|
Center bow roof-bow roof-2 |
4934.417 |
6349.555 |
5553.248 |
41118084.46 |
2027.095 |
0.75 |
360.749 |
1.984 |
OK |
|
Bow roof-2-rear roof |
5796.975 |
2524.365 |
3448.625 |
15857352.52 |
2027.095 |
0.75 |
404.92 |
1.565 |
OK |
then,
Snow load Prediction formula
Qr = [Iy x t2] / [α x s x [(Rx + Ry)/2]2 x 10-8]
Note: The Qr value given over here is correct. There was a typo error in the formula given in the video.
Where
α = My x Lx2 x 10-12 , My = Y(Ly-Y)
Judgement condition = Qr ≥ 3.1
250 ≤ s ≤ 380
t = Roof plate thickness [mm]
Ly = Distance between the front and rear roof Rails on the Vehicle along with 0Y[mm]
Length of Roof panel with the center point between Roof rail Front /Rear as the reference point of the front and the rear.
Lx = Distance between the Left and Right end of the roof on the Roof BOW [mm]
Width of the roof panel exposed on the surface.
Y = Distance front Front Roof Rail to Roof BOW[mm]
s = Distance for which Roof BOW bears divided load [mm]
s = L1/2 + L2/2
Iy = Geometrical moment of inertia of Roof BOW (Y cross-section )[mm4]
Rx = Lateral direction curvature radius of roof panel Y cross-section on Roof BOW [mm]
Roof panel curvature Radius of the Length Lx in Front view
Ry = Longitudinal Direction curvature radius of the Roof panel X cross-section on Roof BOW [mm]
Roof panel X curvature radius of length s in Side view
|
Postion |
Iy(mm) |
t |
<(alpha) |
s |
(Rx+Ry/2)^2 |
Rx |
Ry |
Qr |
Status |
|
Front roof-bow roof1 |
1.057*10^4 |
0.75 |
0.779 |
471.388 |
103528488.26 |
4028.20 |
16321.59 |
15.63 |
OK |
|
Bow roof1-center bow roof |
7.781*10^4 |
0.75 |
0.827 |
480.964 |
57656245.83 |
4265.38 |
10920.962 |
190.85 |
OK |
|
Center bow roof-bow roof2 |
1.084*10^4 |
0.75 |
0.866 |
503.014 |
25168703.65 |
3772.30 |
6261.384 |
55.61 |
OK |
|
Bow roof2-rear roof |
- |
0.75 |
1.016 |
- |
12801214.56 |
4645.06 |
2510.693 |
- |
- |